Water and hydrocarbon-based resources (e.g., natural gas, crude oil, etc.) are some examples of resources that may be extracted from a subterranean rock formation. Accessing and then extracting such resources may often be made possible by drilling a well in the subterranean rock formation, and extending the well to the site where the natural resource is located. The location of the natural resources may often be very remote from a site of the well surface, and the well may sometimes extend many hundreds, if not thousands, of feet into the subterranean rock formation.
Drilling a well can be a complex and expensive task, and drilling a well in an efficient and cost-effective manner may include balancing a number of criteria. For instance, a well may be created by using a drilling system that includes a drill bit connected to a drill string. Power transmitted along the length of the drill string may be used to rotate the drill bit, and cut into the subterranean rock formation. As the drill bit continues to be used to drill deeper into the subterranean rock formation, the drill bit experiences wear. With increased wear, the drill bit becomes less effective and efficient at drilling into the rock formation. As a result, the rate of penetration of the drilling system may decrease. More power may potentially be supplied to increase the rate of penetration; however, increasing the power also adds cost and can potentially cause the drill bit to wear at an even faster rate. Eventually, the drill bit may be removed from the well and replaced by a new drill bit before continuing to extend a well. Removing and replacing a drill bit adds additional expense by virtue of equipment and power costs, and further increases the time, and thus expense, needed to complete a well. Of course, other factors, including conditions within the well (e.g., fluids, cuttings, etc.) may also affect the efficiency of a drilling system.
Further complicating a determination of how to effectively drill a well, conditions of a well may continually evolve. For instance, the material properties of the subterranean rock formation may change. Further, well geometry and length may affect drilling efficiency. For instance, power may increasingly be lost due to friction, heat, or other causes if the well constricts or turns, or even as the length increases. Continual changes to the drill speed, rate of penetration, weight on bit, supplied power, cutting fluids, and other factors associated with drilling a well may therefore be provided to react to ever-changing conditions.
In addition to the complexities in balancing multiple considerations, reacting to the changing conditions may also be difficult if the conditions themselves are not known. It may be difficult, for instance, to use some sensors within a well simply due to the conditions within the well itself. For instance, the drilling system may experience high vibrational and accelerating forces capable of damaging the sensors. Further, a well may be filled with materials such as cutting fluids, rock cuttings, hydrocarbon fluids, and the like. These materials may be abrasive and can damage the sensors within the well. The harsh conditions may exceed allowable conditions for reliable or prolonged use of some types of sensors. A damaged sensor may provide unreliable results, or no results, thereby making it difficult to accurately understand well conditions. Without a good understanding of conditions within the well, it may also be difficult to balance the considerations needed to most efficiently drill the well.
As a more particular example, power or torque may be measured on a drilling component within the well. Strain gauges are commonly used to measure torque, and use wires attached to a surface where strain is to be measured. To provide an accurate measurement, the wires must be reliably connected, and remain reliably connected, which can be difficult in the harsh conditions within a well. Additionally, the drilling component should have a sufficiently large cross-sectional shape to accommodate large loads. The large cross-sectional shape may, however, make it more difficult for the strain gauge to measure small loads. Adding environmental protection may be used in some cases to protect the strain gauge from the harsh well environment on the exterior of a drilling component, but adds to the size and expense of the strain gauge. Moreover, even when environmentally protected, strain gauges are used after a lengthy calibration process, and even then begin to drift over time unless recalibrated.